1. Field of the Invention
The field of this invention lies within the art of optically encoding through a rotational disc, The rotational disc is provided with radial openings or apertures around its periphery in order to interrupt a light source that is transmitted to a light sensor. The light sensor receives the interrupted light pulses and puts out a pulsed response that is in direct pulsed relationship to the rotation of the disc.
More particularly, the invention involves the utilization of such discs in connected relationship to a track ball, whereby a track ball moves against a shaft to which the disc is connected. The rotation of the track ball in an X and Y direction moves the shaft to effectively cause an output corresponding to the movement of the ball by virtue of the disc rotating in a specific orientation and providing specific pulses to indicate movement of the ball.
2. The Prior Art
The prior art with regard to movement of optical disc encoders in one direction or the other has generally relied upon circuit conditioning components and special masks. Generally, an optical encoder incorporates discs having radial slots or apertures therein. On one side of the disc is a light source, such as light from an incandescent bulb or light emitting diode (LED). On the other side of the disc is a light sensor that receives light that is interrupted by the disc cutting the light. This is due to the spaces between the openings alternately interrupting and allowing the light respectively to pass through the openings of the disc. In this manner, the light source can be interrupted and the light sensor receiving the light can provide for a pulsed output depending upon the number of interruptions which constitute the movement of the disc.
Oftentimes, in order to ascertain the movement in reverse directions of the disc which would constitute movement corresponding to plus or minus directional movement, a mask is utilized. The mask provides segmented output windows or openings with regard to the openings of the disc. Thus, when the disc changes direction, it is provided with either a leading or trailing movement of the light source, depending upon whether the disc is moving in one direction or the other. This movement in one direction or the other causes a respective output which indicates the movement in the minus or plus direction or backwardly and forwardly which corresponds thereto.
The output of the light sensor which corresponds to a trailing or leading output is then conditioned by means of a decoding circuit. The decoding circuit oftentimes must entail the utilization of four discrete chips or integrated circuits. This of course is costly and provides for a degree of difficulty in utilizing the disc or the track ball with regard to its output.
The problem with regard to determining when a disc is turning backwardly or forwardly in a track ball situation or in rotation of a disc by itself devolves down to the point of having to have specialized screens with respect to the disc and/or particular circuitry in order to condition or distinguish and decode the motion of the disc. This involves a significantly more complex series of operations and circuits compared to this invention. In particular, this invention allows for a disc that interferes with a light source to permit pulses to be transmitted to a light sensor which characterizes them as plus or minus, in a backward or forward position. This is provided by means of a unique shutter arrangement.
The foregoing shutter arrangement can be effectively applied to a disc which optically encodes a signal from a light output to a light sensor in a number of different ways. One of the specific configurations herein is one wherein a shutter moves over a light source to either provide a first light sensor with an input from the light source, or which shifts over to another sensor in order to provide an output and a sensing at that particular sensor. by having a light slip clutch engage the shutter so that as the shaft turns, it causes the shutter to move in one direction or the other corresponding to the direction of movement of the shaft. This effectively creates a situation wherein the shutter responds to the movement of the shaft in order to provide for the respective output at the particular sensor which relates to that direction of shaft movement. When the shaft moves in the forward or backward direction which corresponds to a plus or minus direction of the disc, the output thereby corresponds with the respective shaft movement. This is due to the particular channel which corresponds thereto receiving light that has been pulsed by the disc, while the other channel is closed off by the shutter.
The foregoing shutter arrangement can be used for single discs on an optical encoding shaft to provide pulsed outputs corresponding to left and right orientation, positive and negative orientation, or backward and forward orientation, or any other orientation which is derived from respective shaft movement in opposite directions. This can also apply of course to the X and Y component movements of shafts for a track ball. It particularly enhances the output of a track ball in the form of a usable signal that does not have to be conditioned and which does not require separate screening circuitry and discrete orientations with respect to the light pulses.
The invention is a substantial step over the prior art with regard to optical encoders in general, as well as a track ball. The output can be for all uses wherein an optical encoding takes place through a disc in order to provide pulses to a light sensor.